Electrical measuring instrument



Oct, 21, 19300 P. H. CRAHG ELECTRICAL MEASURING INSTRUMENT 3 Sheets-Sheet 1 Filed Aug. 12, 1927 J- HHH/l INVENTOR. 222m ff (7?),

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ATTORNEY ump 5 st 21, 1930. P. H. CRAIG ELECTRICAL MEASURING INSTRUMENTFiled Aug. 12, 1927 3 Sheets-$heet 2 IN V EN TOR.

A TTORNEY Get. 21, 1930. P. H. came 397789795 ELECTRICAL MEASURINGINSTRUMENT Filed Aug. 12. 1927 s Sheets-Sheet 5 II 0 Ta a W '"1 W 4 /411:21.15!

effect, Corbino effect, or

.nomena.

latented Oct. 21, 1930 UNITED STATES PATENT OFFICE rum a. exam, orCINCINNATI, 01110 ELECTRIGAL MEASURING INSTRUMENT Application filedAugust '12, 1927. Serial no. 212,585.

' Another object of my invention is to provide, a meter for readingalternating currents and voltages where the possibility of burning outthe meter is extremely remote so that a rugged instrument is-secured.

Still another object of my invention is to provide a circuit arrangementfor a measur ing instrument, wherein the transverse current effect in ametallic film may be measured for unknown potential difference along thelongitudinal axis of the metallic film, the meter in the circuit throughthe transverse axis of the film being calibrated inaccordance with theHall eifect produced by the passage of the longitudinal current throughthe A further object of my invention is to provide a Hall efiectapparatus for measuring both current and voltage in an electricalcircuit for determining consumption of power in watts.

()ther and further objects of my invention reside in the circuitarrangements described in the specification hereinafter following byreference to the accompanying drawings wherein:

Figure 1 illustrates the type of metallic film used in securing therequired Hall effect for actuating the measuring instru ment employed inthe circuit arrangement ofmy invention; Fig. 2 is a diagrammatic viewand the magnetic flux; and

of the measuring instrument of my invention arranged in a circuit fordetermining the value of an alternating current supplied to a loadcircuit; Fig. 3 shows the circuit arrangement of my invention used inthe measuring instrument for determining voltage across an alternatingcurrent line s stem; Fig. 4 shows the circuit arrangement y which themeter of my invention maybe used interchangeably for measuring valuesboth of current and voltage; Fig. 5 illustrates a'circuit arrangementand a modified form of voltage and current measuring device constructedin accordance with my invention; Fig. 6 illustrates the circuitarrangement of my invention as applied to a wattmeter; Fig. 7 shows acircuit arrangement embodying the principles of my invention havingcapacitative reactance arranged in the input circuit for predeterminingthe flux relations between the longitudinal current and the magneticflux across the metallic films; Fig. 8 illustrates a photographicallyprepared Hall effect member having a tuned input circuit; Fig. 9illustrates a meter circuit wherein the flux between the pole facesconstituting the magnetic field may be suitably controlled; Fig. 10illustrates a circuit arrangement having an external shunt across theHall efiect device with inductive reactance for controlling therelationship between the lon itudinal current Fig. 11 showscharacteristic curves illustrating the operation of the apparatus of myinvention.

My invention makes use of the Hall ef- :fect, Corbino effect and similarelectromagnetic phenomena for the rectification of alternating currentsand the impression of the rectified current upon a meter which iscalibrated in accordance with the Hall effect.

The Hall efiect consists, briefly, of an electromagnetic phenomenaobservable when a strip or film of metal carrying a longitudinal currentI, (Fig. 1) is placed in a magnetic field perpendicular to the lane ofsuch a strip, a transverse potential di erence being set up between theedges (2', a of the strip, this difli'erence of potential beingapproximately, under normal conditions, represented by the formula:

E=the transverse potential dlflerence;

where I=the current (Ion tudinal) through thestrip;

d=the thickness 0 the strip; H=the magnetic field strengt The Corbinoefiect is similar to the Hall efiect, except that a radial current isproduced in a circular disc subjected to a magnetic field perpendicularto the plane of the disc.

I have described the Hall efiect in more detail in my copendingapplication Ser. N 0. 121,394, filed July 9, 1926, and in my BritishLetters Patent No. 274,112, accepted March 1, 1928 and French LettersPatent No. 639,801, dated July 19, 1927. In the said application andpatents I have shown various circuits for utilizing the Hall efiect,Corbino efl'ect and similar electromagnetic phenomena whereinv amultiplicity of conductive films are subjected to the passage ofelectromagnetic lines of force which extend substantially perpendicularto the plane ofthe films. the films being connected in an electricalcircuit whereby the longitudinal current is caused to flow through thefilms for deriving a current, which in the case of polygonal shapedplates is transverse to the longitudinal current and is known as Halleffect while in the case of circular disks there is a circularatorycurrent known as the Corbino effect.

I have discovered that if a plate or film of metal such as bismuth,tellurium, bismuthantimony alloy, or any other metal alloy, be connectedas shown in the drawings, the device will act as an electrical rectifierof impressed alternating currents. I connect the metallic films orplates along their longitudinal axes with the circuit in which the unknown value of current or potential difi'erence is to be measured. Theresulting rectified energy existent across the transverse axes of thefilms is conveyed to a meter circuit for securing a proportionaldeflection of the meter by reason of the Hall efiect? for themeasurement of the current or potential difference across thelongitudinal axes of the films or plates. Hall efiect may be observedwhen the magnetic field is in any direction with respect to the platesexcept when the magnetic field is parallel to the plates, but alongitudinal change of resistance results even in this latter case.

Referring to the drawings, Fig. 1 illustrates one of the films or platesby which the Hall efiect-is'measured by the indicating meter. Thealternating current from the cir cuit wherein the characteristics of theenergy is to be measured is sent through the strips along thelongitudinal axes represented by d, 0. In one-half of the cycle, thecurrent flows in the direction 0 to (1, while in the other half of thecycle,-the direction of the current is planes and insulated one from theother with their longitudinal axes connected in parallel and theirtransverse axes connected 1n serles. An electromagnetic field isproduced perpendicular to the films and is constituted by electromagnets1 and 2 having their windings connected in series. The transverse axesof the films which are connected in series are connected to theterminals of the direct curcator 4 thereon arranged to.move over'a scale5 which is calibrated in proportion to the,

Hall effect produced in the films proportional to the currents in thecircuit 6. The circuit 6 is shown connected to any suitable form of loadrepresented at 7. For measuring current from the circuit 6, theapparatus of my invention is connected in series with the load so thatthe circuit extends through the winding of electromagnet 2, the windingof electromagnet 1 and through the longitudinal axes of the plurality offilms returning to the power supply circuit 6. The Hall efi'ect by whichthe transverse current is produced laterally of the films operates themeasuring instrument 3. w

In Fig. 3 I have shown one of the arrangements of-the apparatus of myinvention for measuring voltage across circuit 6. A resistance 8 isshown inserted in series with the line or an electromagnetic winding onthe electromagnets 1 and 2 may be provided havlot ing an inductivereactance which is large switching devices shown at 11 and 12 forincluding predetermined reactances in the supply line, so that theapparatus can be used in connection with a transformer systemrepresented at 14 to supply such voltage or current across or throughthe longitudinal axes of the films as will permit the proper operationof the indicating meter. The electromagnetic windings 1 and 2 or 9 and10 are provided with laminated magnet cores, and whenthe electromagnetsreach saturation throughout the working range of the meter, the scalereadings at 5 will be directly proportional 2;-

to the current, and this is often true when the cores are not saturated.The plates are desi ned for a predetermined output of Hall e ect, sothat regardless of the value of current sent through the longitudinalaxes of the plates, it is impossible to burn out the direct currentmeter to which the rectifier element is connected. I insure against theburning out of the direct current meter to which the rectifier elementis connected by employing a magnetic core material for theelectromagnetic windings about the films. The transformer system 14 maybe designed to step own the voltage and step up the current, or viceverse. to whatever values are required. The transformer becomesmagnetically saturated and may have a sufiicient ratio between theprimary and secondary terminals to serve as the proper impedance in boththe line circuit and the measuring circuit for securing requiredreadings on the meter.

I may employ a modified method of rectification using the Hall effect,that is, operating on the lower portion of the permeability curve of thecore material. That is, either the core of the transformer 1 1 or thecores of the electromagnetic systems 1-2 or 910. By use of thedissymmetry of the permeability curve partial rectification may beobtained without connecting the electromagnetic system and the filmsorplates in series.

In Fig. 5 I have shown the Hall effect plates consisting of metallicmembers 15 10- cated side by side and connected laterally by portions16. The electromagnetic systems comprise windings 17 and 18 connected inseries and with the longitudinal axis of each of the plate members 15 bymeans of conductor 19 which connects to the ends of the plate members15, and the other ends of the plate members 15 are connected throughconductor 20 with the input circuit. Windings 21 and 22 forming part ofthe electromagnetic system are also connected in series with thelongitudinal axis of the plates 15. The two independent windings arebonded at 23 and form a voltage input circuit, with terminals at 24 anda current input circuit with terminals at 25 which may be convenientlyconnected to the input circuit for measuring voltage or current on thesame instrument which may be suitably calibrated on separate scales forthis purpose.

In Fig. 6 I have shown a wattmeter circuit embodying the principles ofmy invention wherein a magnetic core member 26 has a plurality ofconductive films 27 disposed in parallel relationship and insulated bymeans of separators 28 located between the pole faces thereof. A voltagecoil 21 is disposed on the core structure 26 and connected to thecircuit 6 and load 7 as to measure the voltage across the line. Thelongitudinal axes of the film are disposed in series with the load.

- The Hall effect is directly proportional to the product of thelongitudinal current times the magnetic field intensity. One of thesequantities is supplied by the voltage connection across the line, andthe other is supplied by the current connection in series with the line.From the elementary formula of the Hall effect the output isproportional to the longitudinal current times the magnetic field, andin the arrangement of Fig. 6 the Hall efi'ect output is proportional tothe input voltage times the input current times the power factor (i. e.cos. In this way power may be measured utilizing the Hall eflect.

In Fig. 7 I have illustrated'the location of a capacitative reactance 30in the input circuit of the apparatus which is adjustable topredetermine the flux relationships between the lon itudinal current andthe transverse magnetic field. The capacitative reactance 30 serves totune the inductive reactance of the field windings 1 and 2 to resonancewith the frequency of the current being measured thus making use of thehigher field and plate currents which are produced. For example, if aradio frequencycurrent of 1,000 kilocycles is being measured, condenser30 is adjusted so that the capacitative reactance thus arbi: trarilyadded just balances the inductive re actance of the field winding with aresultant amplified current through the field winding and plates inwhich the Hall effect is produced.

In Fig. 8 I have shownan arrangement of tuned circuit 31 across thewindings 32 and 33 disposed on opposite sides of the Hall eifect grid34. The grid illustrated in Fig. 8 is produced by a photographic processwhere a bismuth plate is etched to provide a plurality of conductivepaths separated one from the other, connected at opposite ends 36 and 37and connected centrally along the transverse aXis thereof, asrepresented at 35. The

condenser 31 serves to tune the inductive reactance of the fieldwindings 32 and 33 for rendering the meter selective to a particularfrequency. While the arrangement in Fig. 7 employs the principle ofresonance, the circuit arrangement in Fig. 8 operates upon the principleof anti-resonance, the result being that in the circuit of Fig. 7 thesource of current must supply the larger resonant current since thissource is in series with the resonant circuit, whereas in Fig. 8, forarelatively small input it is possible to obtain relatively largecurrents flowing in the local resonant circuit which is completedthrough condenser 31 and field windings 32 and 33. It should be notedthat the resonant current is efiective through both field and plates inthe arrangement of Fig. 7 but in the arrangement of Fig. 8 the resonantcurrent is effective only through the field.

In Fig. 9 I have shown the electromagnetic systems 1 and 2 having taps38 and 39 on the inductances which form part of the magnetic field withswitching members and 41 for obtaining a predetermined number of turnsin the circuit. The Hall effect plate has been shown in end view at 15.

In Fig. 10 I have shown the i'nputcircuit of the meter shunted b meansof the external shunt 42 with in uctive-reactance 43 in the inputcircuit for regulating the relation of the longitudinal current withrespect to the magnetic field.

In Fig. 11 I have illustrated the characteristic curves obtained in theoperation of a meter system in accordance with m invention, wherein theHall eifect pro uced by a given current input is shown plotted withrespect to two different scales on the measuring instrument. The curvesin Fig. 11 were plotted while utilizing a circuit arrangement accordinto Fig. 7. Curve A was obtained using all effect films of pure bismuthwhich were formed by rapidly cooling the plates after the metal had beenpoured into the mold in a molten condition. Curve -B was obtained by theuse of plates which had been formed by the slow cooling of impurebismuth plates previously cast in molds. The presence of impuritiestherefore decreases the Hall effect as will be seen from a study of thedifferences between curves Av and B. Therefore, great care must be usedto prevent contamination of the metal while being molded becausepractically any impurity produces much lower outputs. This statement,however, does not apply to small quantities of a few metals as I havefound that eight per cent of antimony added to the bismuth tends toincrease the Hall effect.

It will be understood that the plates used may be disposed either instacked relationship or side by side. The plates may be metal, crystalsor alloys possessing Hall or Corbino effects. I

I have found the measuring instrument of my invention accurate in itsreadings, and

.. rugged and stable in its-operation.

Wherever in the claims I have mentioned Hall effect, I also intend bythis expression to include the Corbino effect. I have used theexpression galvanomagnetic effects to include both the expressions Halleffect and Corbino efiect.

While I have. described my invention in certain of its preferredembodiments, I desire that it be understood that modifications may bemade and that no limitations are intended other than are imposed bythescope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is as follows:

1. An instrument for measuring electrical quantities comprising amultiplicity of metallic films having their longitudinal axes disposedparallel one to another and their weaves transverse axes connected incommon, a circuit whose energy is to be measured, inde pendentconnections for applying voltage to be measured extending from saidcircuit to the ends of the longitudinal axes of said films, and separateconnections for applying current to be measured to the ends of thelongitudinal axes of said films, an indicating meter, and connectionsextending fromthe ends of the transverse axis of each of said films inseries to said indicating meter.

2. The method of measuring electrical quantities, which consists indeveloping a Hall effect in metallic films from the electrical energywhose quantity is equal to the product of the impressed voltagemultiplied by the current flow through the metallic films and inmeasuring the amount of Hall effect thus produced.

3. In an electrical measuring system an indicatingmeter, a circuitresponsive to elecv trical energy whose quantity is to be determined,and a device interposed between said circuit and said indicating meterfor de-- ranged in side by side relationship, each of said films havinglongitudinal and transverse axes, with the longitudinal axes thereofconnected in parallel and the transverse axis thereof connected inseries, an indicating meter connected to thetransverse axes ofsaidmetallic films and means for impressing a voltage to be measuredacross the longitudinal axes of said metallic films and separate meansfor passing current to be measured through the longitudinal axes of saidfilms for generating therein a Hall effect in proportion to the value ofthe product of the impressed electrical quantities depend-' entseparately upon a voltage across a load and current passing to a loadfor deriving a uni-directional current in. the series circuit includingthe transverse axes of said films and actuating said indicating meter.

5. In an electrical measuring system a -direct current meter, a memberpossessing galvanomagnetic effects connected therewith, a magnetic fieldadjacent said member, and means for'controlling the influence of saidmagnetic. field upon. said member in proportion to the product of thevoltage "and current existent in the circuit under measurement. a

6. An electrical measuring system com-- prising a direct current meter,an alternating current circuit, a member possessing galvanomagneticeifects, a pair of electromagnetic windings enclosing said member andcontrollable by the voltage and current impressed thereon from saidalternating current circuit, a circuitous path through saidelectromagnetic windings and said member, variable impedance means forcontrolling the relation between the flux developed by saidelectromagnetic windings and the current through said member,andconnections between said meter and said member for measuring theamplitude of current generated in said member.

7. A measuring instrument comprising a magnet, an electromagneticwindingthereon, a Hall effect plate extending across the field of saidmagnet, a load circuit, connections between said load circuit and saidelectromagnetic winding through the longitudinal axis of said Halleffect plate in series, independent connections between said load andthe longitudinal axis of said Hall effect plate, and a meter forindicating the Hall effect across the transverse axes of said plates.

8. An electrical measuring instrument comprising a magnet, anelectromagnetic windmg thereon, a Hall effect plate disposed in thefield of said magnet, a meter connected across the transverse axis ofsaid Hall effect plate, a load circuit, and independent connectionsbetween said load circuit, said Hall effect plate, and saidelectromagnetic winding, one of said connections impressing thepotential of said load circuit across said electromagnetic winding andthe longitudinal axis of said Hall effect plate in series and the otherof said connections including a series path from said load circuitthrough the longitudinal axis of said Hall effect plate.

9. An electrical measuring instrument comprising a magnetic member, aHall effect plate disposed in the field thereof, a measurmginstrument-connected with the transverse axis of said Hall effectmagnetic winding disposed on said magnetic member, a load circuit,connections for applying the potential of said load circuit across saidelectromagnetic winding, and independen connections for passing thecurrent to said load circuit through the longitudinal axis of said Halleffect plate.

10. An electrical measuring instrument comprising a magnetic member, anelectromagnetic winding disposed thereon, a multiplicity of Hall efiectplates disposed within the field of said magnetic member, said Halleffect plates having their transverse axes connected in series andconnected with a measuring instrument, said Hall effect plates havingtheir longitudinal axes connected in parallel, a load circuit, and meansfor applying the potential of said load circult across saidelectromagnetic Winding and plate, an electrosimultaneousl load circuitlongitudinal In testimo y passing the current to said through theparallel connected axes of said Hall effect ny whereof I aflix m PALMERH.

plates. y signature.

CRAIG.

